Today I've been doing the sums so I can move all non-essential money from my current account into my savings and investments. One of my requirements is that I maintain a 6 month 'emergency fund' that covers all of my expenses in the current account, so I set out to work out how much that is.

First I listed down all of my 'essential' outgoings (with no cutting back, including car, rent, gym, food, broadband, etc), did the sums, and it turns out (before tax) I could survive on a £9k salary (or about £650 per month after tax). If I cut down on the non-essentials, like the gym, downgraded the broadband to 256k, and went PAYG, a £7000 income is sustainable (with £50 a month spare, even). So, assuming I want to live with the comfortable budget instead, that makes £3900 for the emergency fund. Job done! (In reality, it's larger than this, because I wanted to include business expenses 'just in case')

Coincidentally, 35 hours per week at the minimum wage comes out at £9,222 per year, so if it all goes to pot, I can flip burgers and still maintain my non-work lifestyle (even if I end up smelling of fries).